Since november 2011, Kdenlive has moved to the KDE infrastructure. It means that all our translations are now managed by the KDE translation teams. If you want to help translating Kdenlive in your language, the first thing to do is to get in touch with the KDE localization team: http://i18n.kde.org/
There is a team for each language and you can get infos here.
After that, we recommand using the Lokalize tool which was designed to make KDE translations easier. Here is a quick howto, but please Don't forget to contact the translation team for your language so that the work is not done twice.
If you have questions, you can always contect the Kdenlive developers on the Kdenlive mailing list